Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1756643AbdIHRZb (ORCPT <rfc822;w@1wt.eu>);
        Fri, 8 Sep 2017 13:25:31 -0400
Received: from mga02.intel.com ([134.134.136.20]:59458 "EHLO mga02.intel.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1752132AbdIHRZa (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 8 Sep 2017 13:25:30 -0400
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.42,362,1500966000"; 
   d="scan'208";a="1170414543"
Date: Fri, 8 Sep 2017 10:25:29 -0700
From: "Luck, Tony" <tony.luck@intel.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Helge Deller <deller@gmx.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Petr Mladek <pmladek@suse.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Yu, Fenghua" <fenghua.yu@intel.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH 00/14] Fix wrong %pF and %pS printk format specifier
 usages
Message-ID: <20170908172528.qc2vdtxzqh777k6o@intel.com>
References: <20170907004522.GA3885@jagdpanzerIV.localdomain>
 <8b93f9ca-95f6-4e40-1cc8-d1a65833abff@gmx.de>
 <20170907075653.GA533@jagdpanzerIV.localdomain>
 <20170907083207.GC533@jagdpanzerIV.localdomain>
 <667b8849-fb60-a312-2483-505252ff737e@gmx.de>
 <20170907093631.GD533@jagdpanzerIV.localdomain>
 <20170907095119.GE533@jagdpanzerIV.localdomain>
 <0604f27e-24ab-625b-9013-c6c0f4f6acc1@gmx.de>
 <3908561D78D1C84285E8C5FCA982C28F6136C2ED@ORSMSX114.amr.corp.intel.com>
 <20170908061830.GA496@jagdpanzerIV.localdomain>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20170908061830.GA496@jagdpanzerIV.localdomain>
User-Agent: NeoMutt/20170113 (1.7.2)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 665
Lines: 15

On Fri, Sep 08, 2017 at 03:18:30PM +0900, Sergey Senozhatsky wrote:
> if the addr is not in kernel .text, then try dereferencing it and check
> if the dereferenced addr is in kernel .text.

If it really is a function pointer, then we know that it is safe
to dereference. But if it isn't, then maybe not?

If it is a function pointer then dereferening will indeed give
us a .text address. But if it isn't, it might still give us a
.text address (we could reduce the probability of a false hit
by checking that the .text address was exactly on a symbol with
no offset ... but data values that happen to be the addresses of
function entry points are possible).

-Tony